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Hypothyroidism (under active thyroid) is the most common thyroid disorder and usually strikes after age 40. It is more common on women than in men, and affects 6% to 10% of women over the age of 65. The signs and symptoms of an underactive thyroid are:

Hypothyroidism is diagnosed through a simple blood test. Synthetic thyroxine is a safe, effective and low-cost hormone replacement therapy. Dosing must be carefully monitored and the therapy must continue for life.

Synthetic thyroxine is one of the top three most commonly prescribed drugs in North America.

The most common cause of Hypothyroidism is an autoimmune condition called Hashimoto's Thyroiditis in which antibodies and white blood cells attack the thyroid.

(Information based on the Thyroid Foundation of Canada Thyrobulletin, Summer 1998, Vol 19, No. 2)


Hyperthyroidism (overactive thyroid) affects approximately 2% of women and 0.2% of men. The signs and symptoms of an overactive thyroid are:

Hyperthyroidism is diagnosed through a simple blood test. There are three main treatments for overactive thyroid - anti-thyroid drugs, radioiodine therapy and surgery. All are effective, though no treatment ever results in a complete cure.

The most common cause of Hyperthyroidism is and autoimmune condition called Graves' disease in which antibodies stimulate the thyroid uncontrollably.

(Information based on the Thyroid Foundation of Canada Thyrobulletin, Summer 1998, Vol 19, No. 2)

Thyroid Cancer

Thyroid cancer is eminently curable especially if detected early. There are a number of different forms:

The standard treatment involves the surgical removal of thyroid gland. Follicular cancer needs more aggression than Papillary and often requires the removal of lymph nodes. Radioactive Iodine (RAI) treatment is then given to eliminate wandering cells. The treatment is more intense than for treating hyperthyroidism. Patients will not be given thyroxine (T4) replacement in the interim to ensure maximum RAI absorption. They can become SIGNIFICANTLY hypothyroid

Thyroid Nodules

Nodules are simply lumps in the thyroid. There are two basic types of nodule:

Nodules are diagnosed in a number of ways. Thyroid scans are used to determine whether they are hot or cold. Fine Needle Aspiration Biopsy (FNAB) is used to remove cells for analysis, but is inconclusive in up to 30% of cases. Ultrasound Guided FNAB is more reliable. Larger nodules (>3cm) are more likely to be cancerous. A history of neck irradiation implies a higher risk of cancer.

Treatment is very variable. Many patients are simply placed under observation. Thyroxine (T4) can be given to suppress Thyroid Stimulating Hormone (TSH) levels and thereby cause the nodules to shrink. This is called Suppression Therapy. Radioactive Iodine (RAI) is used to destroy hot nodules in some cases and they can also be removed surgically.

Congenital Thyroid Disease

Some children are born with an improperly functioning thyroid gland and some even lack a thyroid gland. In Australia, this situation is usually detected soon after birth through the heel prick test which is administered to all neonates. It is also possible, although rare in Australia, that the mother's diet was deficient in iodine and, as a result, the foetus received too little thyroid hormone in utero.

The standard treatment is thyroid hormone replacement using thyroxine (T4). In many cases this treatment must continue for life.

Iodine Deficiency Disorder

Iodine is needed by the thyroid gland to manufacture thyroid hormones. The iodine needed is normally obtained in food, but the soils in some parts of the world are deficient in iodine and the food does not contain enough iodine. Thyroid hormone production in people living in these areas is suppressed and they suffer Hypothyroid symptoms. The overstimulation of the thyroid gland by the pituitary in an attempt to make more hormone also commonly leads to an enlarged thyroid gland (which is referred to as a goitre).

The iodine deficient regions of the world are generally in elevated and alpine areas far from the sea. Many parts of SE Asia are iodine deficient as is Switzerland. In Australia the iodine deficient areas follow the Great Dividing Range including New England, Canberra, Gippsland and Tasmania. The 'Gippsland Goitre' was well known in years past. Iodine deficiency has been reduced in Australia through iodine supplementation an also through the use of iodine based disinfectants in the dairy industry (which led to increased iodine in milk). There is some recent evidence that iodine deficiency may be returning in Australia as the dairy industry reduces its reliance on iodine based disinfectants.

Iodine deficiency is a very serious problem for newborns and young children because thyroid hormones are essential for growth and the normal development of the brain. Inadequate dietary iodine leads to stunted growth and significant intellectual impairment - which is referred to as Cretinism.

The recommended treatment is iodine supplementation in the diet using iodised salt (the bottles with the green labels) or food rich in iodine. Seafoods, including seaweeds, are high in iodine and are a good source of extra iodine. But care should be exercised because iodine supplementation can be taken too far.

The daily requirement for iodine is very small at some 150 mcg (microgram or millionths of a gram). This means that a person needs about 1 teaspoon full over their whole life. Whilst the normal thyroid gland is tolerant of substantial excess iodine, a diseased or susceptible thyroid is not. Excess iodine can trigger thyroid disease and can make existing conditions worse. A person with a multinodular goitre or Graves’ disease in remission may be precipitated into hyperthyroidism whereas a person with impaired thyroid function may have worsening to hypothyroidism, or goitre growth from excess iodine exposure. A regular intake of the correct amount of iodine is recommended. Some supplements like kelp tablets can contain milligram amounts of iodine and deliver 100's of times the daily requirement so check what you use.

Iodine supplementation is not a substitute for thyroid hormone replacement for those with thyroid function problems or those whose thyroid has been removed.


A goitre is simply a swelling of the thyroid gland. The presence of a goitre is a good indication that something is probably wrong with the thyroid. Iodine deficiency can lead to a goitre as the body tries to compensate by overstimulating the thyroid gland. The inflammation of Hashimoto's thyroiditis frequently also leads to a goitre. The overstimulation of the thyroid gland by Graves' disease antibodies can also lead to a goitre. Cancer or the growth of nodules can also produce a goitre. The cause of the goitre should be determined before appropriate treatment can begin.

Disclaimer: All materials provided by Thyroid Australia are for information purposes only and do not constitute medical advice.

(c) Copyright 1998, Thyroid Foundation of Canada, Hypothyroidism and Hyperthyroidism
Please consult Thyroid Foundation of Canada for permission to use.

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